A. Field of the Invention
The present invention relates in general to power management, and more particularly, to a method and apparatus for regulating the power consumption of a portable battery-operated electronic device. The present invention has particular application to portable radiotelephones used to communicate with terrestrial cellular or satellite wireless telephony systems.
B. Description of Relevant Art
In a portable battery operated electronic device, such as a radiotelephone, aggressive power management is needed in order to maximize battery-life. A common method of managing (more specifically, reducing) power consumption is to periodically place the subject device into a reduced functionality/power state. This reduced functionality/power state is generally referred to as xe2x80x9csleep mode.xe2x80x9d The device is typically roused from its reduced power state by an external event such as a timer or an external interrupt. Often the device can be placed in a number of reduced power states/levels, ranging from full-on to full-off. In the lower power states, however, very few external interrupt sources are still enabled.
The hardware components of a portable electronic device may be segregated and packaged as separate modular units that communicate with one another in carrying out the overall hardware functionality of the device. An electronic device that has more than one modular unit will typically have one or more communication paths between the modules. If the modules are relatively sophisticated components (e.g., where each module has its own microprocessor), each module can control its own power management states. However, some coordination between the modules is necessary to ensure correct operation of each module, as well as maximum total power savings. And, if communication between a given pair of modules can be initiated by either module, then each module must have the capability to rouse the other from a deep sleep state. In the deepest sleep state, the normal communications channels between modules are most likely shut down, thus requiring another mechanism by which one module can rouse another.
A specific example of a modular portable battery operated electronic device of the type described above is Motorola""s Satellite Series 9500 Portable Telephone for use on the Iridium System (hereinafter xe2x80x9cmulti-mode phonexe2x80x9d). The primary modular component of the multi-mode phone is its base phone unit, which provides the main communication conduit between the user and the satellite-based telephony system. Various cellular cassette modules may be plugged into the base phone unit, with each cellular cassette module providing a communication conduit to a particular cellular system. For example a particular plug-in cassette is available that follows U.S. cellular standards, while another different plug-in cassette is available that follows European cellular standards. The base phone unit is essentially a complete radiotelephone including microprocessor, display, microphone, speakers and keypad. Each cellular cassette is also a substantially complete radiotelephone having the essentially the same components as the base phone unit minus the display and key pad.
Accordingly, as both the base phone unit and the cellular cassette are fairly sophisticated devices, both can consume a considerable amount of power. Thus, the multi-mode phone must employ power management strategies to reduce the amount of power consumed. Stated simply, when the multi-mode phone is not doing anything, it must go into a low power state, and, when it subsequently needs to do something, it must be aroused from its low power state. Facilitating power management is more straightforward in a conventional cellular phone that is controlled by a single microprocessor and does not have the modular cassette structure of a multi-mode phone. However, as typical multi-mode phones have two relatively sophisticated modules each having its own microprocessor, implementing power management becomes more complicated. More particularly, because the two modules in a multi-mode phone often need to talk to one another, there is a need to coordinate xe2x80x9csleep statesxe2x80x9d between the base phone module and the cellular cassette module so one can awaken the other prior to sending a communication from one to the other. For example, if both the base phone and the cellular cassette are in a sleep state, and a cellular call comes into the cellular cassette, the cellular cassette needs to be able to rouse the base phone from its sleep state in order to process the cellular call. Also, the base phone unit must be able to rouse the cellular cassette from its sleep state when there user attempts to place a cellular call.
In normal operation, the base phone and the cellular cassette communicate with one another through an asynchronous serial interface. However, the asynchronous serial interface is typically disabled when the base phone and/or the cellular cassette is in its lowest power saving state (other than the xe2x80x9coffxe2x80x9d state). Accordingly, another pathway for communicating so-called xe2x80x9cwake upxe2x80x9d signals between the modules is needed. A straightforward implementation is to provide handshaking wire connections between the modules that are dedicated to passing wake-up signals between the modules.
In general, there is a need to pass four signals between the modules. Each module must be able to send a xe2x80x9cwake upxe2x80x9d signal to the other module. Each module must also be able to send an xe2x80x9cawakexe2x80x9d signal to the other module in response to having received a wake up signal. This would require four handshaking connections/lines between the modules. An example of a handshaking protocol that uses four handshaking signals transmitted across four connections/lines for modem related operations is the RTS/CTS handshaking described in the EIA RS-232C specification.
As applied to modular portable radiotelephone devices, cost and size benefits may be realized by reducing the number connections/lines between the device""s modules. Accordingly, cost and size benefits may be achieved by providing a handshaking protocol that requires fewer handshaking connections/lines.
The present invention provides a method and apparatus that generates and transmits handshaking signals between two peer devices using relatively few transmission lines. A device and method embodying the present invention includes an apparatus that controls power management for two devices. The apparatus includes a first module/device having a controller that controls power management protocols for the first device, the first devices""s power management protocols including at least one reduced power state. The apparatus further includes a second module/device having a controller that controls power management protocols for the second device, the second device""s power management protocols including at least one reduced power state.
No more than two handshaking signal lines are connected between the first device and the second device. The handshaking signal lines include a first handshaking signal line that carries a first handshaking signal from said first device to said second device, along with a second handshaking signal line that carries a second handshaking signal from said second device to said first device. The first device""s power management protocols generate said first handshaking signal, and the second device""s power management protocols generate said second handshaking signal.
The first handshaking signal, when received by said second device at a predetermined time, commands said second device to come out of its at least one reduced power state, and the first handshaking signal, when received by said second device in another predetermined sequence, also informs said second device that said first device is out of its at least one reduced power state.
The second handshaking signal, when received by said first device as part of a predetermined sequence, commands said first device to come out of its at least one reduced power state, and the second handshaking signal, when received by said first device as part of another predetermined sequence, also informs said first device that said second device is out of its reduced power state.
The above-described apparatus may also include data signal lines connecting said first device to said second device. The first handshaking signal is determined based on the state of various events, and on the state of various signals. The second handshaking signal may also be determined based on the state of various events, and on the state of various signals.
The invention itself, together with further objects and attendant advantages, will best be understood by reference to the following detailed description, taken in conjunction with the accompanying drawings.